The matrix proteins of bones and teeth play key roles in the structure and function of these tissues. Our objective in this investigation is to study the structure, and function of these macromolecules and to understand the regulation of their expression. The structure of the bone and tooth matrix proteins has been studied by constructing recombinant cDNA libraries from bone or ameloblast cell mRNA. cDNA encoding several bone and tooth matrix proteins was isolated using expression vectors and mono-specific antisera directed against individual bone and ameloblast proteins. The clones were used to determine the primary structure and mode of expression of the genes in cultured cells and in intact tissue. The corresponding genomic DNA has also been isolated and used to determine the intron-exon organization of these genes and the elements that potentially regulate their expression during development.